In dentistry a variety of devices are available which allow for preparation and/or application of dental materials in a dentist's practice. In particular for preparation of materials that are typically used at larger amounts, like for example dental impression materials, devices have been developed that provide for automatic dispensing from packages and/or for mixing of such materials. An exemplary device for mixing and dispensing a dental impression material is for example available under the designation 3M™ ESPE™ Pentamix™ from 3M ESPE AG, Germany. Typically such a device allows for two material components to be simultaneously supplied from a package through a mixer where they are mixed. Often the devices provide for continuously extruding the components through a mixer, where the components are mixed as the components flow through the mixer and released from an outlet.
The devices further typically have a motor driven piston for extruding the material from a container. A variety of different drive concepts have been proposed for driving the piston at a relatively high force as it may be required for appropriately dispensing the dental material.
For example EP 1 700 639 discloses a device for dispensing a flowable substance. The device comprises at least one force transmitting member (for example a push-pull chain) adapted to transmit a pushing force in a direction toward or opposite the substance and which can be gathered non-linearly.
U.S. Pat. No. 6,168,052 discloses an electrically driven dispensing appliance having an electric drive which acts via drive screws on thrust plates for dispensing material from cartridges. The drive screws are axially stationary and are in action relationship with a slide bearing said thrust plates. The electric drive comprises a first gear motor for a drive under high load during advance and relief, and a second motor for the drive under lower load during the retracting and fast advance motions.
Although there are a variety of devices on the market which provide for automatic mixing and dispensing there is still a desire to minimize costs for manufacturing of such devices and for providing the devices with maximized reliability.